Image reading device and image reading method

ABSTRACT

There are provided a line sensor (110) including two first sensor pixel rows (111a, 111b) and a second sensor pixel row (112a); an image obtaining unit (140) to obtain, from electrical signals obtained by scanning an original in a sub-scanning direction with the two first sensor pixel rows (111a, 111b), two first read image data items, and obtain, from electrical signals obtained by scanning the original in the sub-scanning direction with the second sensor pixel row (112a), a second read image data item; and an image processor (150) to incorporate one or more pixel data items of one or more pixels included in an interval between the two first sensor pixel rows (111a, 111b) out of the second read image data item into the two first read image data items, thereby generating a line image data item in which the one or more pixels in the interval are not vacant.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is based on PCT filing PCT/JP2020/003612, filedJan. 31, 2020, the entire contents of which are incorporated herein byreference.

TECHNICAL FIELD

The present disclosure relates to an image reading device and an imagereading method.

BACKGROUND ART

Contact image sensors that scan originals as subjects of image readingapplied to copiers, scanners, facsimile machines, or the like with linesensors that are one-dimensional imaging devices and generate image datarepresenting images of the originals have been put to practical use.

A contact image sensor includes multiple sensor pixel rows arrangedlinearly in a main scanning direction. Each of the multiple sensor pixelrows includes multiple imaging elements arranged linearly in the mainscanning direction at predetermined intervals. Each of the multipleimaging elements corresponds to pixel data indicating a value of onepixel on a one-to-one basis.

No imaging elements are disposed between adjacent two of the multiplesensor pixel rows. Thus, when the imaging elements are arranged with asmall pitch, a lack of pixel data occurs at a boundary between the twosensor pixel rows.

Thus, for example, Patent Literature 1 discloses a device thatinterpolates lacking pixel data from neighboring pixel data by signalprocessing.

CITATION LIST Patent Literature

Patent Literature 1: Japanese Patent Application Publication No.2003-101724 (page 8 and FIG. 3 )

SUMMARY OF INVENTION Technical Problem

However, in the conventional device, when the sensor pixel rows have ahigh resolution, the number of pixels corresponding to a lacking portionis more than one, and the interpolation cannot be performed with highaccuracy.

Thus, an object of the present disclosure is to make it possible toaccurately read an image of an original even in the case of usinghigh-resolution sensor pixel rows.

Solution to Problem

An image reading device according to an aspect of the present disclosureincludes: a line sensor including at least one set including two firstimaging element rows and a second imaging element row, the two firstimaging element rows each including a plurality of imaging elements thatare arranged in a main scanning direction and obtain electrical signalsof pixels in the main scanning direction, the two first imaging elementrows being arranged with a first interval therebetween in the mainscanning direction, the second imaging element row including a pluralityof imaging elements that are arranged in the main scanning direction andat least obtain one or more electrical signals of one or more pixelsincluded in the first interval, the two first imaging element rows andthe second imaging element row being arranged with a predeterminedsecond interval therebetween in a sub-scanning direction that is adirection perpendicular to the main scanning direction; an imageobtaining unit to obtain, from electrical signals obtained by scanningan original in the sub-scanning direction with the two first imagingelement rows, two first read image data items including pixel data itemsof pixels corresponding to the respective two first imaging elementrows, and obtain, from electrical signals obtained by scanning theoriginal in the sub-scanning direction with the second imaging elementrow, a second read image data item including pixel data items of pixelscorresponding to the second imaging element row; and an image processorto generate a line image data item in which the one or more pixels inthe first interval are not vacant, by incorporating one or more pixeldata items of the one or more pixels included in the first interval outof the second read image data item into the two first read image dataitems.

An image reading method according to an aspect of the present disclosureincludes: obtaining two first read image data items from electricalsignals obtained by scanning an original with two first imaging elementrows in the sub-scanning direction, the two first imaging element rowseach including a plurality of imaging elements that are arranged in amain scanning direction and obtain electrical signals of pixels in themain scanning direction, the two first imaging element rows beingarranged with a first interval therebetween in the main scanningdirection, the two first read image data items including pixel dataitems of pixels corresponding to the respective two first imagingelement rows; obtaining a second read image data item from electricalsignals obtained by scanning the original with a second imaging elementrow in the sub-scanning direction, the second imaging element rowincluding a plurality of imaging elements that are arranged in the mainscanning direction and at least obtain one or more electrical signals ofone or more pixels included in the first interval, the second read imagedata item including pixel data items of pixels corresponding to thesecond imaging element row; and generating a line image data item inwhich the one or more pixels in the first interval are not vacant, byincorporating one or more pixel data items of the one or more pixelsincluded in the first interval out of the second read image data iteminto the two first read image data items.

Advantageous Effects of Invention

One or more aspects of the present disclosure make it possible toaccurately read an image of an original even in the case of usinghigh-resolution sensor pixel rows.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram illustrating a configuration of a main portionof an image reading device according to a first embodiment.

FIG. 2 is a block diagram illustrating configurations of imageprocessors of first and second embodiments.

FIG. 3 is a block diagram schematically illustrating a configuration ofan interpolation image data generator of the first embodiment.

FIGS. 4A and 4B are block diagrams illustrating hardware configurationexamples.

FIG. 5 is a schematic diagram illustrating an example of an arrangementof a line sensor and an original.

FIG. 6 is a schematic diagram for explaining an area in which each offirst sensor pixel rows and second sensor pixel rows reads an image fromthe original.

FIGS. 7A and 7B are schematic diagrams for explaining processing of animage read from each of the first sensor pixel rows and second sensorpixel rows.

FIG. 8 is a schematic diagram for explaining second read image dataitems and sub corrected image data items.

FIG. 9 is a schematic diagram for explaining a process in an image dataseparator.

FIGS. 10A and 10B are schematic diagrams for explaining a process ofcorrecting displacements in the main scanning direction in a mainscanning direction position corrector.

FIGS. 11A to 11F are schematic diagrams for explaining a process in anoverlap region image data processor.

FIG. 12 is a block diagram illustrating a configuration of a mainportion of an image reading device according to a second embodiment.

FIG. 13 is a partially enlarged view for explaining a line sensor of thesecond embodiment.

FIG. 14 is a block diagram schematically illustrating a configuration ofan interpolation image data generator.

DESCRIPTION OF EMBODIMENTS First Embodiment

FIG. 1 is a block diagram illustrating a configuration of a main portionof an image reading device 100 according to a first embodiment.

The main portion of the image reading device 100 according to the firstembodiment includes a line sensor 110, a signal reader 120, an imagecorrector 130, and an image processor 150. Although not illustrated inFIG. 1 , the image reading device 100 may include other portions, suchas a light source that illuminates an original to be read, a conveyorthat conveys the original or line sensor 110, and a controller thatcontrols operation of the entire device. In the first embodiment, it isassumed that the conveyor conveys the original.

The line sensor 110 includes imaging elements that convert lightreflected from the original into electrical signals. Electrical signalsof pixels are obtained by the imaging elements.

The line sensor 110 includes first sensor pixel rows 111 a to 111 c thatare first imaging element rows including multiple imaging elementsarranged in a main scanning direction, and second sensor pixel rows 112a to 112 c that are second imaging element rows including multipleimaging elements arranged in the main scanning direction.

In the first embodiment, each of the first sensor pixel rows 111 a to111 c is formed by a first sensor chip that is a single sensor chip.Also, each of the second sensor pixel rows 112 a to 112 c is formed by asecond sensor chip that is a single sensor chip.

A first interval that is a predetermined interval exists between thefirst sensor pixel row 111 a and the first sensor pixel row 111 b, andbetween the first sensor pixel row 111 b and the first sensor pixel row111 c. The first interval is an interval greater than or equal to onepixel.

In the line sensor 110, the second sensor pixel rows 112 a to 112 c aredisposed at positions spaced by one or more lines from the first sensorpixel rows 111 a to 111 c in a sub-scanning direction perpendicular tothe main scanning direction. The interval between the first sensor pixelrows 111 a to 111 c and the second sensor pixel rows 112 a to 112 c willalso be referred to as a second interval.

Also, the first sensor pixel rows 111 a to 111 c and second sensor pixelrows 112 a to 112 c are arranged so that at their ends in the mainscanning direction, regions OR1 to OR5 including one or more pixelsoverlap each other in the main scanning direction.

That is, the second sensor pixel row 112 a is configured so that it canat least obtain electrical signal(s) of pixel(s) included in theinterval between the first sensor pixel row 111 a and the first sensorpixel row 111 b, and the second sensor pixel row 112 b is configured sothat it can at least obtain electrical signal(s) of pixel(s) included inthe interval between the first sensor pixel row 111 b and the firstsensor pixel row 111 c.

Moreover, the second sensor pixel row 112 a includes imaging elementsalso outside the interval between the first sensor pixel row 111 a andthe first sensor pixel row 111 b in the main scanning direction so thatit can obtain electrical signals of pixels outside both ends of theinterval in the main scanning direction. The second sensor pixel row 112b includes imaging elements also outside the interval between the firstsensor pixel row 111 b and the first sensor pixel row 111 c in the mainscanning direction so that it can obtain electrical signals of pixelsoutside both ends of the interval in the main scanning direction.

The first sensor pixel rows 111 a to 111 c are equal in number of pixelsper one sensor pixel row, and the second sensor pixel rows 112 a to 112c are also equal in number of pixels per one sensor pixel row. Pixelintervals that are intervals in the main scanning direction betweenpixels of each of the first sensor pixel rows 111 a to 111 c and each ofthe second sensor pixel rows 112 a to 112 c are equal.

In this embodiment, the number of pixels per one sensor pixel row of thefirst sensor pixel rows 111 a to 111 c is less than that of the secondsensor pixel rows 112 a to 112 c. The number of pixels per one sensorpixel row of the second sensor pixel rows 112 a to 112 c may be lessthan that of the first sensor pixel rows 111 a to 111 c, or they may beequal.

When the original is conveyed, the first sensor pixel rows 111 a to 111c start to read the original earlier, and the second sensor pixel rows112 a to 112 c read image data of the original the time required toconvey the original later. That is, the first sensor pixel rows 111 a to111 c are disposed upstream of the second sensor pixel rows 112 a to 112c in the sub-scanning direction. Although in FIG. 1 , the line sensor110 is constituted by six sensor pixel rows, it is sufficient that theline sensor 110 include three or more sensor pixel rows arranged atdifferent sub-scanning positions, e.g., at least one set including twofirst sensor pixel rows and one second sensor pixel row.

The signal reader 120 converts values corresponding to the electricalsignals obtained by the line sensor 110 into image data indicating themon a pixel-by-pixel basis.

The image corrector 130 corrects image data input thereto for variationin performance between the sensor pixel rows or the like, and outputscharacteristic corrected image data that is image data resulting fromthe correction, as read image data.

As above, the signal reader 120 and image corrector 130 constitute animage obtaining unit 140 that obtains, from the electrical signalsobtained by the line sensor 110, the read image data indicating a valueof each pixel.

For example, the electrical signals detected by the first sensor pixelrows 111 a to 111 c and second sensor pixel rows 112 a to 112 c are readby the signal reader 120, and converted into first image data items EYato EYc and second image data items OYa to OYc. The first image dataitems EYa to EYc and second image data items OYa to OYc are corrected bythe image corrector 130, and the corrected image data items are outputas first read image data items EHa to EHc and second read image dataitems OHa to OHc.

That is, the image obtaining unit 140 obtains, from the electricalsignals obtained by scanning the original in the sub-scanning directionwith the first sensor pixel rows 111 a to 111 c, the first read imagedata items EHa to EHc including pixel data items of corresponding pixelsof the first sensor pixel rows 111 a to 111 c. Also, the image obtainingunit 140 obtains, from the electrical signals obtained by scanning theoriginal in the sub-scanning direction with the second sensor pixel rows112 a to 112 c, the second read image data items OHa to OHc includingcorresponding pixel data items of the second sensor pixel rows 112 a to112 c.

The image processor 150 processes the first read image data items EHa toEHc and second read image data items OHa to OHc provided from the imagecorrector 130.

For example, the image processor 150 inserts the pixel data items of thepixels included in the first intervals, in which the first sensor pixelrows 111 a to 111 c are not disposed, out of the second read image dataitems OHa to OHc, into corresponding spaces between the first read imagedata items EHa to EHc, thereby generating a line image data item inwhich the pixels in the first intervals are not vacant.

Specifically, the image processor 150 corrects a positional displacementin the sub-scanning direction in the first read image data items EHa toEHc and second read image data items OHa to OHc, generates image data ofan image without image overlap in the main scanning direction, andoutputs line-by-line line image data representing an image read from theoriginal.

FIG. 2 is a block diagram illustrating a configuration of the imageprocessor 150.

The image processor 150 includes a sub displacement correction amountsetter 151, an image memory 152, a sub-scanning direction positioncorrector 153, a main overlap processing amount setter 154, an imagedata separator 155, an interpolation image data generator 156, and animage connector 157.

The sub displacement correction amount setter 151 receives input ofsub-scanning direction displacement amount information indicating thepositional difference in the sub-scanning direction between the firstsensor pixel rows 111 a to 111 c and the second sensor pixel rows 112 ato 112 c of the line sensor 110, and stores the sub-scanning directiondisplacement amount information in a memory 151 a that is a subdisplacement amount storage.

The sub-scanning direction displacement amount information indicates asub-scanning direction displacement amount that is a displacement amountin the sub-scanning direction between each pair overlapping each otherin the main scanning direction in the first sensor pixel rows 111 a to111 c and second sensor pixel rows 112 a to 112 c.

For example, in the example illustrated in FIG. 1 , the sub-scanningdirection displacement amount information indicates a sub-scanningdirection displacement amount between the pair of the first sensor pixelrow 111 a and second sensor pixel row 112 a, a sub-scanning directiondisplacement amount between the pair of first sensor pixel row 111 b andsecond sensor pixel row 112 a, a sub-scanning direction displacementamount between the pair of the first sensor pixel row 111 b and secondsensor pixel row 112 b, a sub-scanning direction displacement amountbetween the pair of the first sensor pixel row 111 c and second sensorpixel row 112 b, and a sub-scanning direction displacement amountbetween the pair of the first sensor pixel row 111 c and second sensorpixel row 112 c.

Then, the sub displacement correction amount setter 151 selects, fromamong the sub-scanning direction displacement amounts indicated by thesub-scanning direction displacement amount information, sub-scanningdirection displacement amount(s) corresponding to each of the first readimage data items EHa to EHc processed by the sub-scanning directionposition corrector 153. Then, the sub displacement correction amountsetter 151 calculates sub-scanning direction displacement correctionamounts obtained by correcting the selected sub-scanning directiondisplacement amounts in accordance with the conveyance speed of theoriginal, and provides the sub-scanning direction displacementcorrection amounts to the sub-scanning direction position corrector 153.

When the sub-scanning direction displacement amounts indicated by thesub-scanning direction displacement amount information are thesub-scanning direction displacement correction amounts, the subdisplacement correction amount setter 151 may provide, as thesub-scanning direction displacement correction amounts, the selectedsub-scanning direction displacement amounts to the sub-scanningdirection position corrector 153.

Measurements of the sub-scanning direction displacement amounts may beperformed inside the image reading device 100, or may be performedoutside the image reading device 100. When the sub-scanning directiondisplacement amounts are measured inside the image reading device 100,the measurements may be performed by a portion, e.g., a sub-scanningdirection displacement amount measurement unit, that is not illustratedin FIG. 1 .

Here, the sub-scanning direction displacement amounts include, inaddition to displacement amounts due to designed positionaldisplacements between the first sensor pixel rows 111 a to 111 c and thesecond sensor pixel rows 112 a to 112 c, displacement amounts due tomounting displacement occurring during the actual mounting to asubstrate or the like. The sub-scanning direction displacement amountsvary depending on the position where the correction is performed, andcan be in decimal fraction units, which are finer than integer unitsthat are pixel units. Also, although the first sensor pixel rows 111 ato 111 c and second sensor pixel rows 112 a to 112 c are preferablyarranged parallel to each other, they are not parallel when mountingdisplacement occurs, and the sub-scanning direction displacement amountmay be different between one end and the other end.

The sub displacement correction amount setter 151 calculates thesub-scanning direction displacement correction amounts depending on acorrection method in the sub-scanning direction position corrector 153,and provides them to the sub-scanning direction position corrector 153.For example, when the sub-scanning direction position corrector 153performs processing on the assumption that the sub-scanning directiondisplacement amount is constant over a sensor pixel row, the subdisplacement correction amount setter 151 calculates an average of thesub-scanning direction displacement amounts at both ends of a targetsensor pixel row, and then calculates the sub-scanning directiondisplacement correction amount. Also, when the sub-scanning directionposition corrector 153 performs correction of the sub-scanning directiondisplacement amount in accordance with the inclinations of the sensorpixel rows, the sub displacement correction amount setter 151 calculatessub-scanning direction displacement correction amounts at predeterminedintervals in the main scanning direction of a target sensor pixel row.

The image memory 152 is a temporary storage that temporarily stores thefirst read image data items EHa to EHc corresponding to the first sensorpixel rows 111 a to 111 c.

For example, the image memory 152 temporarily stores a single-line dataitem that is pixel data items corresponding to a single line in the mainscanning direction of each of the first read image data items EHa toEHc.

The sub-scanning direction position corrector 153 corrects thepositional displacement in the sub-scanning direction between the firstread image data items EHa to EHc and the second read image data itemsOHa to OHc by reading the first read image data items EHa to EHctemporarily stored in the image memory 152, on the basis of thesub-scanning direction displacement correction amounts set from the subdisplacement correction amount setter 151.

For example, the sub-scanning direction position corrector 153 correctsthe displacement in the sub-scanning direction by storing a single-linedata item of each of the first read image data items EHa to EHc in theimage memory 152 and reading the single-line data items from the imagememory 152 in accordance with the time at which the image obtaining unit140 obtains the pixel data items of a corresponding single line of thesecond read image data items OHa to OHc.

Then, the sub-scanning direction position corrector 153 provides theimage data separator 155 with sub corrected image data items and thesecond read image data items that are aligned in the sub-scanningdirection.

The main overlap processing amount setter 154 receives input of mainscanning direction overlap amount information indicating overlap pixelnumbers that are the numbers of pixels overlapping in the main scanningdirection in the first sensor pixel rows 111 a to 111 c and secondsensor pixel rows 112 a to 112 c of the line sensor 110, and stores themain scanning direction overlap amount information in a memory 154 athat is a main overlap amount storage.

The main scanning direction overlap amount information indicates a mainscanning direction overlap amount that is the number of pixelsoverlapping in the main scanning direction between each pair overlappingeach other in the main scanning direction in the first sensor pixel rows111 a to 111 c and second sensor pixel rows 112 a to 112 c.

For example, in the example illustrated in FIG. 1 , the main scanningdirection overlap amount information indicates the number of pixelsincluded in the region OR1 in the first sensor pixel row 111 a and thenumber of pixels included in the region OR1 in the second sensor pixelrow 112 a, the number of pixels included in the region OR2 in the firstsensor pixel row 111 b and the number of pixels included in the regionOR2 in the second sensor pixel row 112 a, the number of pixels includedin the region OR3 in the first sensor pixel row 111 b and the number ofpixels included in the region OR3 in the second sensor pixel row 112 b,the number of pixels included in the region OR4 in the first sensorpixel row 111 c and the number of pixels included in the region OR4 inthe second sensor pixel row 112 b, and the number of pixels included inthe region OR5 in the first sensor pixel row 111 c and the number ofpixels included in the region OR5 in the second sensor pixel row 112 c.

The main overlap processing amount setter 154 selects main scanningdirection overlap amount(s) of the sensor pixel row corresponding to animage data item processed by the image data separator 155 and providesthe image data separator 155 with the corresponding main scanningdirection overlap processing amount(s), and selects main scanningdirection overlap amount(s) of the sensor pixel row corresponding to animage data item processed by the interpolation image data generator 156and provides the interpolation image data generator 156 with thecorresponding main scanning direction overlap processing amount(s).

As with the sub-scanning direction displacement amounts, measurements ofthe main scanning direction overlap amounts may be performed inside theimage reading device 100, or may be performed outside the image readingdevice 100. When the main scanning direction overlap amounts aremeasured inside the image reading device 100, the measurements may beperformed by a portion, e.g., a main scanning direction overlap amountmeasurement unit, that is not illustrated in FIG. 1 .

The main scanning direction overlap amounts include, in addition todesign overlap amounts that are designed amounts of overlaps between thefirst sensor pixel rows 111 a to 111 c and the second sensor pixel rows112 a to 112 c, mounting overlap amounts that are overlap amountsoccurring during the actual mounting to a substrate or the like. Themain scanning direction overlap amounts vary depending on the positionwhere the correction is performed, and can be in decimal fraction units,which are finer than integer units that are pixel units. When adisplacement occurs in the main scanning direction during mounting of asensor pixel row, the main scanning direction overlap amount may bedifferent between one end and the other end of the sensor pixel row.

Here, in the first embodiment, it is assumed that the main scanningdirection overlap amount information indicates the overlap amounts indecimal fraction units. The main overlap processing amount setter 154provides the interpolation image data generator 156 with fractional mainscanning direction overlap processing amounts that indicate overlapamounts in decimal fraction units. Also, the main overlap processingamount setter 154 provides the image data separator 155 with integermain scanning direction overlap processing amounts obtained by changingthe overlap amounts in decimal fraction units indicated by the mainscanning direction overlap amount information into overlap amounts ininteger units depending on a processing method in the interpolationimage data generator 156.

The image data separator 155 separates the second read image data itemsoutput from the sub-scanning direction position corrector 153, in themain scanning direction, on the basis of the integer main scanningdirection overlap processing amounts set from the main overlapprocessing amount setter 154, thereby generating overlapping image dataitems corresponding to portions overlapping the sub corrected image dataitems and non-overlapping image data items that do not overlap the subcorrected image data items. Here, the non-overlapping image data itemsseparated from the second read image data items OHa and OHb obtainedfrom the second sensor pixel rows 112 a and 112 b make pixel data itemsof pixels in the intervals between the first sensor pixel rows 111 a to111 c.

Then, the image data separator 155 provides the overlapping image dataitems and sub corrected image data items to the interpolation image datagenerator 156, and provides the non-overlapping image data items to theimage connector 157.

The interpolation image data generator 156 generates main correctedimage data items by correcting displacements in the main scanningdirection occurring between the overlapping image data items and the subcorrected image data items.

Also, the interpolation image data generator 156 generates interpolationimage data items by adjusting the pixel data items of overlap pixelsthat are pixels of the main corrected image data items overlapping thesecond read image data items in the main scanning direction, between themain corrected image data items and the second read image data items.Here, the interpolation image data generator 156 modifies pixel valuesof portions of the main corrected image data items overlapping thesecond read image data items (overlapping image data items) on the basisof the overlapping image data items as needed, and generatesinterpolation image data items to be connected to the non-overlappingimage data items.

FIG. 3 is a block diagram schematically illustrating a configuration ofthe interpolation image data generator 156.

The interpolation image data generator 156 includes an overlap regionimage data extractor 156 a, a main scanning direction position corrector156 b, and an overlap region image data processor 156 c.

The overlap region image data extractor 156 a extracts, from theoverlapping image data items and sub corrected image data items inputthereto, the sub corrected image data items, provides the sub correctedimage data items to the main scanning direction position corrector 156b, and provides the overlapping image data items to the overlap regionimage data processor 156 c.

The main scanning direction position corrector 156 b corrects positionaldisplacements of the sub corrected image data items in decimal fractionunits in the main scanning direction, and provides the corrected subcorrected image data items as the main corrected image data items to theoverlap region image data processor 156 c.

The overlap region image data processor 156 c corrects pixel values ofpixels of portions of the main corrected image data items overlappingthe overlapping image data items as needed, and provides image dataitems resulting from the processing as the interpolation image dataitems to the image connector 157 illustrated in FIG. 2 .

Returning to FIG. 2 , the image connector 157 connects thenon-overlapping image data items and interpolation image data items inaccordance with the arrangement order in the main scanning direction inthe original, and generates a line image data item on a line-by-linebasis.

Part or the whole of the signal reader 120, image corrector 130, andimage processor 150 described above can be implemented by a memory 10and a processor 11, such as a central processing unit (CPU), thatexecutes a program stored in the memory 10, as illustrated in FIG. 4A,for example. Such a program may be provided via a network, or may bestored and provided in a recording medium. Thus, such a program may beprovided as a program product, for example.

Also, part or the whole of the signal reader 120, image corrector 130,and image processor 150 can be implemented by processing circuitry 12,such as a single circuit, a composite circuit, a programmed processor, aparallel-programmed processor, an application specific integratedcircuit (ASIC), or a field programmable gate array (FPGA), asillustrated in FIG. 4B, for example.

As above, the signal reader 120, image corrector 130, and imageprocessor 150 can be implemented by a processing circuit network.

Next, an operation of the image reading device 100 in the firstembodiment will be described.

In the first embodiment, it is assumed that the line sensor 110 of theimage reading device 100 and an original 160 are placed as illustratedin FIG. 5 .

Also, it is assumed that the original 160 is conveyed from a side onwhich the first sensor pixel rows 111 a to 111 c of the line sensor 110are disposed, to a side on which the second sensor pixel rows 112 a to112 c are disposed.

Although it is possible that the line sensor 110 is moved from an upperportion toward a lower portion of the original 160, it is assumed in thefirst embodiment that the reading is performed by conveying the original160.

FIG. 6 is a schematic diagram for explaining an area in which each ofthe first sensor pixel rows 111 a to 111 c and second sensor pixel rows112 a to 112 c reads an image from the original 160.

The first sensor pixel rows 111 a to 111 c and second sensor pixel rows112 a to 112 c are arranged so that their ends in the main scanningdirection overlap a little. Thus, the areas read by the sensor pixelrows overlap as illustrated in FIG. 6 .

In FIG. 6 , reading areas R1 a to R1 c respectively correspond to theareas read by the first sensor pixel rows 111 a to 111 c, and readingareas R2 a to R2 c respectively correspond to the areas read by thesecond sensor pixel rows 112 a to 112 c.

In the image reading device 100, while the original 160 is conveyed, thesignal reader 120 receives the electrical signals output from the sensorpixel rows, on a line-by-line basis.

Since the first sensor pixel rows 111 a to 111 c and second sensor pixelrows 112 a to 112 c are spaced from each other in the sub-scanningdirection, the image data items read at the same time are from differentpositions of the original 160 in the sub-scanning direction. Thus, asillustrated in FIG. 7A, the first image data items EYa to EYc and secondimage data items OYa to OYc, which are different in read time, areoutput from the signal reader 120.

A required image correction is performed by the image corrector 130 foreach sensor pixel row, and the first read image data items EHa to EHcand second read image data items OHa to OHc, which are different in readtime as with the first image data items EYa to EYc and second image dataitems OYa to OYc, are output (see FIG. 7B).

The first read image data items EHa to EHc and second read image dataitems OHa to OHc are input to the sub-scanning direction positioncorrector 153 of the image processor 150.

Since the first read image data items EHa to EHc have read start timesin the sub-scanning direction earlier than those of the second readimage data items OHa to OHc, the sub-scanning direction positioncorrector 153 distinguishes between the first read image data items EHato EHc and the second read image data items OHa to OHc. Then, to absorbthe difference in read time in the sub-scanning direction, thesub-scanning direction position corrector 153 temporarily stores thefirst read image data items EHa to EHc in the image memory 152.

It is assumed that the read image data items are associated with thesensor pixel rows by a method such as assigning a separate input port toeach sensor pixel row or adding data items identifying the sensor pixelrows to the image data items.

After that, by reading, from the image memory 152, the first read imagedata items EHa to EHc from the first lines on a line-by-line basis insynchronization with inputs of the valid line images at the first linesof the second read image data items OHa to OHc after the original 160 isconveyed by amounts corresponding to the numbers of lines correspondingto the sub-scanning direction displacement amounts between the firstsensor pixel rows 111 a to 111 c and the second sensor pixel rows 112 ato 112 c, it is possible to output image data items whose positions inthe sub-scanning direction have been corrected.

The sub displacement correction amount setter 151 sets, from thesub-scanning direction displacement amount information, sub-scanningdirection displacement correction amount(s) corresponding to each of thefirst read image data items EHa to EHc and second read image data itemsOHa to OHc input to the sub-scanning direction position corrector 153,in the sub-scanning direction position corrector 153. The sub-scanningdirection displacement correction amount(s) may vary between the sensorpixel rows. Thus, the sub displacement correction amount setter 151 setsthe sub-scanning direction displacement correction amount(s) dependingon which sensor pixel row is a target of the correction processing inthe sub-scanning direction position corrector 153.

The sub-scanning direction position corrector 153 corrects thepositional displacement between the images by determining, based on thesub-scanning direction displacement correction amounts set therein,times to read the first read image data items EHa to EHc temporarilystored in the image memory 152 and eliminating the time difference inthe sub-scanning direction between the first read image data items EHato EHc and the second read image data items OHa to OHc. When thesub-scanning direction displacement correction amounts are integers, itis only required to synchronize the starts of readings of the first readimage data items EHa to EHc from the image memory 152. However, when thesub-scanning direction displacement correction amounts are decimalfractions, the sub-scanning direction position corrector 153 alsoapplies resampling processing. A common interpolation process may beused for the resampling processing, and the sub-scanning directionposition corrector 153 may perform resampling processing on either orboth of the first read image data items EHa to EHc and the second readimage data items OHa to OHc.

The sub-scanning direction position corrector 153 adjusts starting timesof readings of the image data items from the image memory 152 in view ofthe used process and the input times of the second read image data itemsOHa to OHc.

In this manner, as illustrated in FIG. 8 , sub corrected image dataitems ESa to ESc in which the read time difference in the sub-scanningdirection of the first read image data items EHa to EHc, i.e., thepositional displacement of the images in the sub-scanning direction, hasbeen eliminated, and the second read image data items OHa to OHc areoutput from the sub-scanning direction position corrector 153 on aline-by-line basis in a state in which they still overlap in the mainscanning direction.

The image data separator 155 separates, from the second read image dataitems OHa to OHc, the overlapping image data items corresponding to theportions overlapping the sub corrected image data items ESa to ESc onthe basis of the integer main scanning direction overlap processingamounts set from the main overlap processing amount setter 154, andprovides the overlapping image data items and sub corrected image dataitems ESa to ESc to the interpolation image data generator 156. Also,the image data separator 155 provides the image connector 157 with thenon-overlapping image data items that are partial image data itemsremaining after the separation of the overlapping image data items fromthe second read image data items OHa to OHc.

FIG. 9 is a schematic diagram for explaining a process in the image dataseparator 155.

The image data separator 155 separates, from the second read image dataitem OHa, an overlapping image data item OCa1 overlapping the subcorrected image data item ESa and an overlapping image data item OCa2overlapping the sub corrected image data item ESb.

Also, the image data separator 155 separates, from the second read imagedata item OHb, an overlapping image data item OCb1 overlapping the subcorrected image data item ESh and an overlapping image data item OCb2overlapping the sub corrected image data item ESc.

Moreover, the image data separator 155 separates, from the second readimage data item OHc, an overlapping image data item OCc1 overlapping thesub corrected image data item ESc.

Then, the image data separator 155 provides the interpolation image datagenerator 156 with the sub corrected image data items ESa, ESb, and EScand the overlapping image data items OCa1, OCa2, OCb1, OCb2, and OCc1,as an output A.

Also, the image data separator 155 provides the image connector 157 witha non-overlapping image data item ONa, remaining after the separation ofthe overlapping image data items OCa1 and OCa2 from the second readimage data item OHa, a non-overlapping image data item ONb remainingalter the separation of the overlapping image data items OCb1 and OCb2from the second read image data item OHb, and a non-overlapping imagedata item ONc remaining after the separation of the overlapping imagedata item OCc1 from the second read image data item OHc, as an output B.

In the interpolation image data generator 156, the overlap region imagedata extractor 156 a provides the main scanning direction positioncorrector 156 b with the sub corrected image data items Esa, ESb, andESc, and provides the overlap region image data processor 156 c with theoverlapping image data items OCa1, OCa2, OCb1, OCb2, and OCc1, out ofthe sub corrected image data items ESa, ESb, and ESc and overlappingimage data items OCa1, OCa2, OCb1, OCb2, and OCc1 provided thereto.

FIGS. 10A and 10B are schematic diagrams for explaining a process ofcorrecting displacements in the main scanning direction in the mainscanning direction position corrector 156 b.

Here, it is assumed that as illustrated in FIG. 10A, 4 pixels at a rightend of the first sensor pixel row 111 b and 4 pixels at a left end ofthe second sensor pixel row 112 b overlap in an overlap region R2 b-L,and 5.2 pixels at a right end of the second sensor pixel row 112 b and5.2 pixels at a left end of the first sensor pixel row 111 c overlap inan overlap region R2 b-R.

In the example illustrated in FIG. 10A, there is a positionaldisplacement in decimal fraction units in the overlap region R2 b-R. Themain scanning direction position corrector 156 b corrects the positionaldisplacement in decimal fraction units, thereby outputting a maincorrected image data item EMc as illustrated in FIG. 10B.

In the overlap region R2 b-L, since there is no positional displacementin decimal fraction units, the main scanning direction positioncorrector 156 b performs no correction. Thus, a main corrected imagedata item EMb is the same as the sub corrected image data item ESb.

Here, a common interpolation process may be used for the process ofcorrecting a positional displacement in decimal fraction units, as withthe sub-scanning direction position corrector 153.

In the example illustrated in FIGS. 10A and 10B, the main scanningdirection position corrector 156 b shifts the sub corrected image dataitem ESc by 0.2 pixels to the right. However, the first embodiment isnot limited to such an example. For example, the main scanning directionposition corrector 156 b may shift it by 0.8 pixels to the left and makethe second read image data item OHb and main corrected image data itemEMc overlap by 6 pixels.

Here, the main overlap processing amount setter 154 should calculate theinteger main scanning direction overlap processing amounts set in theimage data separator 155, depending on the processing method in the mainscanning direction position corrector 156 b.

The main scanning direction position corrector 156 b may correct thepositional displacements in the main scanning direction only for thepixels overlapping the overlapping image data items, out of the pixelsof the sub corrected image data items.

As above, the main scanning direction position corrector 156 b providesthe overlap region image data processor 156 c with the main correctedimage data items obtained by correcting the pixel displacements indecimal fraction units in the main scanning direction.

The overlap region image data processor 156 c corrects pixel values ofthe pixels of the main corrected image data items that overlap theoverlapping image data items, as needed, and provides the imageconnector 157 illustrated in FIG. 2 with image data items resulting fromthe processing as the interpolation image data items.

FIGS. 11A to 11F are schematic diagrams for explaining a process in theoverlap region image data processor 156 c.

Here, there will be described an example in which processing isperformed using the main corrected image data items EMb and EMc andoverlapping image data items OCb1 and OCb2.

As illustrated in FIG. 11A, the main corrected image data item EMboverlaps the overlapping image data item OCb1 by 4 pixels in the overlapregion R2 b-L, and the main corrected image data item EMc overlaps theoverlapping image data item OCb2 by 5 pixels in the overlap region R2b-R.

FIGS. 11B to 11F are graphs illustrating a ratio of mixing the pixels inthe overlap region R2 b-L of the main corrected image data item EMb andthe pixels of the overlapping image data item OCb1, and a ratio ofmixing the pixels in the overlap region R2 b-R of the main correctedimage data item EMc and the pixels of the overlapping image data itemOCb2.

In each graph, the horizontal axis represents pixel positions in themain scanning direction, and the vertical axis is the mixing ratio thattakes a value from 0 to 1. The solid line represents the proportion ofthe pixel value of the second read image data item OHb, and the dottedline represents the proportion of the main corrected image data itemsEMb and EMc. The sum of the proportions at each pixel position is set tobe equal to 1.

FIG. 11B is an example in which the pixels in the overlap region R2 b-Lof the main corrected image data item EMb are replaced with the pixelsof the overlapping image data item OCb1, and the pixels in the overlapregion R2 b-R of the main corrected image data item EMc are replacedwith the pixels of the overlapping image data item OCb2.

FIG. 11C is an example in which the pixels in the overlap region R2 b-Lof the main corrected image data item EMb are left as they are, and thepixels in the overlap region R2 b-R of the main corrected image dataitem EMc are left as they are.

FIG. 11D is an example in which the pixels in the overlap region R2 b-Lof the main corrected image data item EMb are mixed with the pixels ofthe overlapping image data item OCb1 at a ratio of 1:1, and the pixelsin the overlap region R2 b-R of the main corrected image data item EMcare mixed with the pixels of the overlapping image data item OCb2 at aratio of 1:1.

FIG. 11E is a first example in which the pixels in the overlap region R2b-L of the main corrected image data item EMb are mixed with the pixelsof the overlapping image data item OCb1 such that the proportion of thepixel of the overlapping image data item OCb1 increases toward an end ofthe main corrected image data item EMb, and the pixels in the overlapregion R2 b-R of the main corrected image data item EMc are mixed withthe pixels of the overlapping image data item OCb2 such that theproportion of the overlapping image data item OCb2 increases toward anend of the main corrected image data item EMc.

In the first example, the rate of increase in the proportion of theoverlapping image data item OCb2 is constant toward the end of the maincorrected image data item EMb or toward the end of the main correctedimage data item EMc.

FIG. 11F is a second example in which the pixels in the overlap regionR2 b-L of the main corrected image data item EMb are mixed with thepixels of the overlapping image data item OCb1 such that the proportionof the pixel of the overlapping image data item OCb1 increases towardthe end of the main corrected image data item EMb, and the pixels in theoverlap region R2 b-R of the main corrected image data item EMc aremixed with the pixels of the overlapping image data item OCb2 such thatthe proportion of the overlapping image data item OCb2 increases towardthe end of the main corrected image data item EMc.

In the second example, the rate of increase in the proportion of theoverlapping image data item OCb2 increases toward the end of the maincorrected image data item EMb or toward the end of the main correctedimage data item EMc.

In FIGS. 11B and 11C, since there is no pixel data mixing in the overlapregions, image data with relatively less blur is obtained. However, forexample, when the original slightly waves while being conveyed, adifference in image quality, such as a difference in image brightness,that cannot be sufficiently corrected by the image corrector 130 mayoccur between the first image data items EYa to EYc and the second imagedata items OYa to OYc, due to variation in how it is illuminated, or thelike.

When image data items of the overlap regions are generated by simplyaveraging as in FIG. 11D, only the overlap regions have pixel data itemsdifferent from any of the second read image data item OHb and maincorrected image data items EMb and EMc, a difference in image qualityoccurs between the second read image data item OHb and the maincorrected image data items EMb and EMc, and the positions of the imagedata changes in the main scanning direction are noticeable.

Thus, by finely setting the mixing ratio on a pixel-by-pixel basis andsmoothly mixing the image data items in the overlap regions as in FIG.11E or 11F, the positions of the image data changes in the main scanningdirection can be made unnoticeable.

The overlap region image data processor 156 c may prepare multiplesettings of the mixing ratio as illustrated in FIGS. 11B to 11F andswitch the mixing ratio in accordance with an original contentdiscrimination signal (not illustrated) from the outside.

That is, the overlap region image data processor 156 c may have multiplemethods for adjusting the pixel data items of the overlap pixels and beconfigured so that it can select a method for adjusting the pixel dataitems of the overlap pixels from among the multiple methods.

In this manner, interpolation image data items ERa to ERc correspondingto the main corrected image data items EMa to EMc are output from theoverlap region image data processor 156 c. Excluding the overlapregions, the pixel data items of the interpolation image data items ERato ERc are the same as the pixel data items of the main corrected imagedata items EMa to EMc, regardless of the content of the processing inthe overlap region image data processor 156 c.

The image connector 157 connects the interpolation image data items ERato ERc output from the interpolation image data generator 156 and thenon-overlapping image data items ONa to ONc output from the image dataseparator 155, in the main scanning direction, and generates a lineimage data item.

The image reading device 100 repeats image reading on a line-by-linebasis while conveying the original 160 in the sub-scanning direction, asdescribed above, and eventually outputs image data of an image that isthe same as that of the original 160 illustrated in FIG. 5 .

In the first embodiment, it is described that the separation andextraction of image data are performed by the image data separator 155and overlap region image data extractor 156 a, which are separatelyprovided. However, the image data separator 155 may further performsorting of image data and provide the same function.

In the first embodiment, in the sub-scanning direction positioncorrector 153, the first read image data items EHa to EHc are corrected.However, the second read image data items OHa to OHc may be corrected,or both the first read image data items EHa to EHc and second read imagedata items OHa to OHc may be corrected.

In the first embodiment, the line sensor 110 is described as amonochrome sensor constituted by one pair of lines arranged in thesub-scanning direction. However, even when the line sensor 110 is acolor sensor constituted by multiple pairs of lines arranged in thesub-scanning direction, it is possible to obtain a color image with highaccuracy by performing the same processing as described above for eachpair.

As described above, with the image reading device 100 according to thefirst embodiment, even in the case of using a high-resolution sensor, itis possible to accurately read an image without lack of pixel databetween sensor pixel rows.

Also, with the image reading device 100 according to the firstembodiment, since the number of pixels of each of the first sensor pixelrows 111 a to 111 c is less than that of each of the second sensor pixelrows 112 a to 112 c, it is possible to reduce the capacity of the imagememory 152 as compared to the case of using sensor pixel rows having thesame number of pixels.

Also, with the image reading device 100 according to the firstembodiment, it is possible to correct the positional displacements inthe sub-scanning direction and main scanning direction while changingthe displacement amount depending on the position of the target sensorpixel row.

Also, with the image reading device 100 according to the firstembodiment, since the position correction in the sub-scanning directionand the position correction in the main scanning direction are performedon only the image data items read from the first sensor pixel rows 111 ato 111 c having less pixels, it is possible to reduce the image dataarea in which high-frequency components are reduced due to thecorrection processing.

Also, with the image reading device 100 according to the firstembodiment, by providing multiple methods for generating image dataitems of the overlap regions in the overlap region image data processor156 c and switching between them, it is possible to generate image dataappropriate for the content of the original.

Also, with the image reading device 100 according to the firstembodiment, by limiting the area subject to the overlap region imagedata generation process in the interpolation image data generator 156 tothe overlap regions R2 b-L and R2 b-R, it is possible to reduce theimage data area in which high-frequency components are reduced due tothe mixing.

Second Embodiment

FIG. 12 is a block diagram illustrating a configuration of a mainportion of an image reading device 200 according to a second embodiment.

The main portion of the image reading device 200 according to the secondembodiment includes a line sensor 210, a signal reader 120, an imagecorrector 130, and an image processor 250.

The signal reader 120 and image corrector 130 of the image readingdevice 200 according to the second embodiment are the same as the signalreader 120 and image corrector 130 of the image reading device 100according to the first embodiment. Thus, also in the second embodiment,the signal reader 120 and image corrector 130 constitute an imageobtaining unit 140.

In the line sensor 110 of the first embodiment, the first sensor pixelrows 111 a to 111 c and second sensor pixel rows 112 a to 112 c arespaced an arbitrary number of pixels from each other in the sub-scanningdirection such that their ends in the main scanning direction overlapeach other by about several pixels.

On the other hand, the line sensor 210 of the second embodiment isconfigured by arranging, in the main scanning direction, a sensor chip213 a including a pair of a first sensor pixel row 211 a and a secondsensor pixel row 212 a that are adjacent two rows, a sensor chip 213 bincluding a pair of a first sensor pixel row 211 b and a second sensorpixel row 212 b that are adjacent two rows, and a sensor chip 213 cincluding a pair of a first sensor pixel row 211 c and a second sensorpixel row 212 c that are adjacent two rows.

FIG. 13 is a partially enlarged view for explaining the line sensor 210of the second of embodiment.

The first sensor pixel row 211 a and second sensor pixel row 212 aoverlap in an overlap region R3 a-R in the main scanning direction.

The first sensor pixel row 211 b and second sensor pixel row 212 aoverlap in an overlap region R3 b-L in the main scanning direction.

The first sensor pixel row 211 b and second sensor pixel row 212 boverlap in an overlap region R3 b-R in the main scanning direction.

The first sensor pixel row 211 c and second sensor pixel row 212 boverlap in an overlap region R3 c-L in the main scanning direction.

The first sensor pixel row 211 c and second sensor pixel row 212 coverlap in an overlap region R3 c-R in the main scanning direction.

Although in FIG. 13 , the line sensor 210 is constituted by the sixsensor pixel rows, i.e., the three sensor chips 213 a to 213 c, it issufficient that the line sensor 210 include at least one sensor chip. Inthis case, it is necessary to add a sensor chip in the first embodimentincluding only one first sensor pixel row to the line sensor. However,when the line sensor 210 is formed by using only the sensor chip in thesecond embodiment, the line sensor 210 needs to include at least twosensor chips.

The number of pixels in the main scanning direction of each of the firstsensor pixel rows 211 a to 211 c in FIG. 13 is less than the number ofpixels in the main scanning direction of each of the second sensor pixelrows 212 a to 212 c.

Moreover, the number of pixels in the main scanning direction of each ofthe second sensor pixel rows 212 a to 212 c is greater than the numberof pixels corresponding to peripheral portions around the first sensorpixel rows 211 a to 211 c where no pixel can be arranged in the mainscanning direction and that occur during manufacturing of the sensorchips 213 a to 213 c, and is a necessary and sufficient number of pixelsfor execution of processing on pixel data items in the overlap regionsR3 a-R, R3 b-L, R3 b-R, R3 c-L, and R3 c-R in an overlap region imagedata processor 156 c regardless of pixel displacement in the mainscanning direction.

In the second embodiment, the number of pixels in the main scanningdirection of each of the first sensor pixel rows 211 a to 211 c is 14.

A distance between the first sensor pixel rows 211 a to 211 c and thesecond sensor pixel rows 212 a to 212 c in the sub-scanning direction isset to be as small as possible so that the capacity of the image memory152 can be minimized.

Here, a description will be made by using the sensor chip 213 billustrated in FIG. 13 .

In the sensor chip 213 b, since the first sensor pixel row 211 b andsecond sensor pixel row 212 b are disposed on the same base, such as asemiconductor substrate, a main scanning direction overlap amount and asub-scanning direction displacement amount in the overlap region R3 b-Rbetween the first sensor pixel row 211 b and the second sensor pixel row212 b in the same chip can be regarded as fixed values, as compared tothe case of arranging two sensor pixel rows in the first embodiment.Moreover, in the case of arrangement on the same base, it is possible toarrange the sensor pixel rows with relatively high accuracy, and it isalso possible to perform control so that a main scanning directionoverlap amount between the first sensor pixel row 211 b and the secondsensor pixel row 212 b is in integer pixel units. The same applies tothe sensor chips 213 a and 213 c.

Also, in the overlap region R3 b-L across a boundary between the sensorchips 213 a and 213 b, e.g., the second sensor pixel row 212 a and thefirst sensor pixel row 211 b, positional displacement may occur duringmounting of the sensor chips. Thus, it is difficult to set main scanningdirection overlap amounts in all the boundaries between the sensor chipsto fixed values. However, when a reading resolution in the main scanningdirection of the image reading device 200 is as high as 1200 dpi or 2400dpi, a pixel pitch of the sensor pixel rows is as small as 21.2 to 10.6μm, and the main scanning direction overlap amounts are likely to be ininteger units.

Thus, in the second embodiment, the main scanning direction overlapamounts are in integer units.

As illustrated in FIG. 2 , the image processor 250 of the secondembodiment includes a sub displacement correction amount setter 151, animage memory 152, a sub-scanning direction position corrector 153, amain overlap processing amount setter 254, an image data separator 155,an interpolation image data generator 256, and an image connector 157.

The main overlap processing amount setter 254 receives input of mainscanning direction overlap amount information indicating the numbers ofpixels overlapping in the main scanning direction in sensor pixel rowends of the first sensor pixel rows 211 a to 211 c and second sensorpixel rows 212 a to 212 c of the line sensor 210, and stores the mainscanning direction overlap amount information in a memory 254 a that isa main overlap amount storage.

The main overlap processing amount setter 254 selects main scanningdirection overlap amount(s) of the sensor pixel row corresponding to animage data item processed by the image data separator 155 and providesthe image data separator 155 with the corresponding main scanningdirection overlap processing amount(s), and selects main scanningdirection overlap amount(s) of the sensor pixel row corresponding to animage data item processed by the interpolation image data generator 256and provides the interpolation image data generator 256 with thecorresponding main scanning direction overlap processing amount(s).

The main scanning direction overlap amounts include, in addition todesign overlap amounts that are designed amounts of overlaps between thefirst sensor pixel rows 211 a to 211 c and the second sensor pixel rows212 a to 212 c, mounting overlap amounts that are overlap amountsoccurring during the actual mounting to a substrate or the like. In thesecond embodiment, the main scanning direction overlap amounts are ininteger units, as described above.

Then, the main overlap processing amount setter 254 provides theinterpolation image data generator 256 and image data separator 155 withinteger main scanning direction overlap processing amounts indicatingthe main scanning direction overlap amounts in integer units.

The interpolation image data generator 256 generates interpolation imagedata items by adjusting the pixel data items of overlap pixels that arepixels of the sub corrected image data items overlapping the second readimage data items in the main scanning direction, between the subcorrected image data items and the second read image data items. Forexample, the interpolation image data generator 256 modifies pixelvalues of portions of the sub corrected image data items overlapping thesecond read image data items (overlapping image data items) on the basisof the overlapping image data items as needed, and generatesinterpolation image data items to be connected to the non-overlappingimage data items.

FIG. 14 is a block diagram schematically illustrating a configuration ofthe interpolation image data generator 256.

The interpolation image data generator 256 includes an overlap regionimage data extractor 156 a and the overlap region image data processor156 c.

In the second embodiment, since the overlap amounts in the main scanningdirection are in integer units, the main scanning direction positioncorrector 156 b in the first embodiment is unnecessary.

Thus, the overlap region image data processor 156 c performs processingby using the sub corrected image data items instead of the maincorrected image data items.

The content of processing by the overlap region image data extractor 156a and overlap region image data processor 156 c in the second embodimentis the same as the content of processing by the overlap region imagedata extractor 156 a and overlap region image data processor 156 c inthe first embodiment.

As above, in the second embodiment, by using the sensor chips 213 a, 213b, and 213 c to form the line sensor 210, it is possible at least to seta positional displacement in the main scanning direction in the overlapregion between the two sensor pixel rows included in each of the sensorchips 213 a, 213 b, and 213 c to be in integer units, and thus it ispossible to eliminate the processing regarding positional displacementcorrection in the main scanning direction.

Also, with the image reading device 200 according to the secondembodiment, since the number of pixels of the first sensor pixel rows211 a to 211 c disposed on the upstream side is a necessary andsufficient number of pixels for execution of processing by the overlapregion image data processor 156 c as compared to the second sensorpixel, rows 212 a to 212 c, it is possible to reduce the number ofpixels in the main scanning direction of the overlap regions subject tocorrection or mixing. Thus, it is possible to reduce the image data areain which high-frequency components are reduced.

Although in FIG. 13 , each of the sensor chips 213 a to 213 c has a wideshape obtained by combining two rectangles in the sub-scanningdirection, it is sufficient that two sensor pixel rows can be formed atpositions spaced a predetermined number of pixels from each other ineach of the main scanning direction and sub-scanning direction and thesensor pixel rows can be arranged with longitudinal directions of thesensor pixel rows in the main scanning direction, and they may haveeasy-to-manufacture shapes, such as shapes separated by straight lines.

REFERENCE SIGNS LIST

100, 200 image reading device, 110, 210 line sensor, 111 a, 111 b, 111c, 211 a, 211 b, 211 c first sensor pixel row, 112 a, 112 b, 112 c, 212a, 212 b, 212 c second sensor pixel row, 213 a, 213 b, 213 c sensorchip, 120 signal reader, 130 image corrector, 140 image obtaining unit,150, 250 image processor, 151 sub displacement correction amount setter,152 image memory, 153 sub-scanning direction position corrector, 154main overlap processing amount setter, 155, 255 image data separator,156, 256 interpolation image data generator, 156 a overlap region imagedata extractor, 156 b main scanning direction position corrector, 156 coverlap region image data processor, 157 image connector.

The invention claimed is:
 1. An image reading device comprising: a linesensor including at least one set including two first imaging elementrows and a second imaging element row, the two first imaging elementrows each including a plurality of imaging elements that are arranged ina main scanning direction and obtain electrical signals of pixels in themain scanning direction, the two first imaging element rows beingarranged with a first interval therebetween in the main scanningdirection, the second imaging element row including a plurality ofimaging elements that are arranged in the main scanning direction and atleast obtain one or more electrical signals of one or more pixelsincluded in the first interval, the two first imaging element rows andthe second imaging element row being arranged with a second intervaltherebetween in a sub-scanning direction that is a directionperpendicular to the main scanning direction; and processing circuitryto obtain, from electrical signals obtained by scanning an original inthe sub-scanning direction with the two first imaging element rows, twofirst read image data items including pixel data items of pixelscorresponding to the respective two first imaging element rows, toobtain, from electrical signals obtained by scanning the original in thesub-scanning direction with the second imaging element row, a secondread image data item including pixel data items of pixels correspondingto the second imaging element row, and to generate a line image dataitem in which the one or more pixels in the first interval are notvacant, by incorporating one or more pixel data items of the one or morepixels included in the first interval out of the second read image dataitem into the two first read image data items, wherein the plurality ofimaging elements of the second imaging element row include imagingelements arranged outside the first interval in the main scanningdirection so that the plurality of imaging elements of the secondimaging element row are capable of obtaining electrical signals ofpixels outside both ends of the first interval in the main scanningdirection, and the processing circuitry is configured to temporarilystore a single-line data item that is pixel data items corresponding toa single line in the main scanning direction of each of the two firstread image data items, to generate two sub corrected image data items inwhich a displacement in the sub-scanning direction generated due to thesecond interval between each of the two first read image data items andthe second read image data item has been corrected from each of the twofirst read image data items, by reading the temporarily storedsingle-line data items in accordance with a time at which the processingcircuitry obtains pixel data items of a corresponding single line of thesecond read image data item, to set main scanning direction overlapprocessing amounts by selecting overlap amounts in the main scanningdirection of the first imaging element rows, to separate, from thesecond read image data item, a non-overlapping image data item that isthe one or more pixel data items of the one or more pixels included inthe first interval, on a basis of the main scanning direction overlapprocessing amounts, to generate two main corrected image data items fromthe two sub corrected image data items by correcting a positionaldisplacement in the main scanning direction between each of the two subcorrected image data items and the second read image data item byshifting positions of one or more pixels included in each of the two subcorrected image data items, in the main scanning direction in decimalfraction units, to generate two interpolation image data items byadjusting, in each of the two main corrected image data items, one ormore pixel data items of one or more overlap pixels that are one or morepixels overlapping the second read image data item in the main scanningdirection, between the main corrected image data item and the secondread image data item, and to generate the line image data item byconnecting the two interpolation image data items and thenon-overlapping image data item.
 2. An image reading device comprising:a line sensor including at least one set including two first imagingelement rows and a second imaging element row, the two first imagingelement rows each including a plurality of imaging elements that arearranged in a main scanning direction and obtain electrical signals ofpixels in the main scanning direction, the two first imaging elementrows being arranged with a first interval therebetween in the mainscanning direction, the second imaging element row including a pluralityof imaging elements that are arranged in the main scanning direction andat least obtain one or more electrical signals of one or more pixelsincluded in the first interval, the two first imaging element rows andthe second imaging element row being arranged with a second intervaltherebetween in a sub-scanning direction that is a directionperpendicular to the main scanning direction; and processing circuitryto obtain, from electrical signals obtained by scanning an original inthe sub-scanning direction with the two first imaging element rows, twofirst read image data items including pixel data items of pixelscorresponding to the respective two first imaging element rows, toobtain, from electrical signals obtained by scanning the original in thesub-scanning direction with the second imaging element row, a secondread image data item including pixel data items of pixels correspondingto the second imaging element row, and to generate a line image dataitem in which the one or more pixels in the first interval are notvacant, by incorporating one or more pixel data items of the one or morepixels included in the first interval out of the second read image dataitem into the two first read image data items, wherein the plurality ofimaging elements of the second imaging element row include imagingelements arranged outside the first interval in the main scanningdirection so that the plurality of imaging elements of the secondimaging element row are capable of obtaining electrical signals ofpixels outside both ends of the first interval in the main scanningdirection, and the processing circuitry is configured to temporarilystore a single-line data item that is pixel data items corresponding toa single line in the main scanning direction of each of the two firstread image data items, to generate two sub corrected image data items inwhich a displacement in the sub-scanning direction generated due to thesecond interval between each of the two first read image data items andthe second read image data item has been corrected from each of the twofirst read image data items, by reading the temporarily storedsingle-line data items in accordance with a time at which the processingcircuitry obtains pixel data items of a corresponding single line of thesecond read image data item, to separate, from the second read imagedata item, a non-overlapping image data item that is the one or morepixel data items of the one or more pixels included in the firstinterval, to generate two interpolation image data items by adjusting,in each of the two sub corrected image data items, one or more pixeldata items of one or more overlap pixels that are one or more pixelsoverlapping the second read image data item in the main scanningdirection, between the sub corrected image data item and the second readimage data item, and to generate the line image data item by connectingthe two interpolation image data items and the non-overlapping imagedata item.
 3. An image reading method comprising: obtaining two firstread image data items from electrical signals obtained by scanning anoriginal with two first imaging element rows in a sub-scanning directionthat is a direction perpendicular to a main scanning direction, the twofirst imaging element rows each including a plurality of imagingelements that are arranged in the main scanning direction and obtainelectrical signals of pixels in the main scanning direction, the twofirst imaging element rows being arranged with a first intervaltherebetween in the main scanning direction, the two first read imagedata items including pixel data items of pixels corresponding to therespective two first imaging element rows; obtaining a second read imagedata item from electrical signals obtained by scanning the original witha second imaging element row in the sub-scanning direction, the secondimaging element row including a plurality of imaging elements that arearranged in the main scanning direction and at least obtain one or moreelectrical signals of one or more pixels included in the first interval,the two first imaging element rows and the second imaging element rowbeing arranged with a second interval therebetween in the sub-scanningdirection, the second read image data item including pixel data items ofpixels corresponding to the second imaging element row; and generating aline image data item in which the one or more pixels in the firstinterval are not vacant, by incorporating one or more pixel data itemsof the one or more pixels included in the first interval out of thesecond read image data item into the two first read image data items,wherein the plurality of imaging elements of the second imaging elementrow include imaging elements arranged outside the first interval in themain scanning direction so that the plurality of imaging elements of thesecond imaging element row are capable of obtaining electrical signalsof pixels outside both ends of the first interval in the main scanningdirection, and the generating the line image data item includes:temporarily storing a single-line data item that is pixel data itemscorresponding to a single line in the main scanning direction of each ofthe two first read image data items; generating two sub corrected imagedata items in which a displacement in the sub-scanning directiongenerated due to the second interval between each of the two first readimage data items and the second read image data item has been correctedfrom each of the two first read image data items, by reading thetemporarily stored single-line data items in accordance with a time ofobtaining pixel data items of a corresponding single line of the secondread image data item; setting main scanning direction overlap processingamounts by selecting overlap amounts in the main scanning direction ofthe first imaging element rows; separating, from the second read imagedata item, a non-overlapping image data item that is the one or morepixel data items of the one or more pixels included in the firstinterval, on a basis of the main scanning direction overlap processingamounts; generating two main corrected image data items from the two subcorrected image data items by correcting a positional displacement inthe main scanning direction between each of the two sub corrected imagedata items and the second read image data item by shifting positions ofone or more pixels included in each of the two sub corrected image dataitems, in the main scanning direction in decimal fraction units;generating two interpolation image data items by adjusting, in each ofthe two main corrected image data items, one or more pixel data items ofone or more overlap pixels that are one or more pixels overlapping thesecond read image data item in the main scanning direction, between themain corrected image data item and the second read image data item; andgenerating the line image data item by connecting the two interpolationimage data items and the non-overlapping image data item.